apple2js/js/intbasic/decompiler.ts

import { byte, Memory, word } from 'js/types';

const LETTERS =
'                                ' +
' !"#$%&\'()*+,-./0123456789:;<=>?' +
'@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_' +
'`abcdefghijklmnopqrstuvwxyz{|}~ ';

const TOKENS: Record<byte, string> = {
    0x02: '_',
    0x03: ':',
    0x04: 'LOAD',
    0x05: 'SAVE',
    0x06: 'CON',
    0x07: 'RUN',
    0x08: 'RUN',
    0x09: 'DEL',
    0x0A: ',',
    0x0B: 'NEW',
    0x0C: 'CLR',
    0x0D: 'AUTO',
    0x0E: ',',
    0x0F: 'MAN',
    0x10: 'HIMEM:',
    0x11: 'LOMEM:',
    0x12: '+',
    0x13: '-',
    0x14: '*',
    0x15: '/',
    0x16: '=',
    0x17: '#',
    0x18: '>=',
    0x19: '>',
    0x1A: '<=',
    0x1B: '<>',
    0x1C: '<',
    0x1D: 'AND',
    0x1E: 'OR',
    0x1F: 'MOD',
    0x20: '^',
    0x21: '+',
    0x22: '(',
    0x23: ',',
    0x24: 'THEN',
    0x25: 'THEN',
    0x26: ',',
    0x27: ',',
    0x28: '\'',
    0x29: '\'',
    0x2A: '(',
    0x2B: '!',
    0x2C: '!',
    0x2D: '(',
    0x2E: 'PEEK',
    0x2F: 'RND',
    0x30: 'SGN',
    0x31: 'ABS',
    0x32: 'PDL',
    0x33: 'RNDX',
    0x34: '(',
    0x35: '+',
    0x36: '-',
    0x37: 'NOT',
    0x38: '(',
    0x39: '=',
    0x3A: '#',
    0x3B: 'LEN(',
    0x3C: 'ASC(',
    0x3D: 'SCRN(',
    0x3E: ',',
    0x3F: '(',
    0x40: '$',
    0x41: '$',
    0x42: '(',
    0x43: ',',
    0x44: ',',
    0x45: ';',
    0x46: ';',
    0x47: ';',
    0x48: ',',
    0x49: ',',
    0x4A: ',',
    0x4B: 'TEXT',
    0x4C: 'GR',
    0x4D: 'CALL',
    0x4E: 'DIM',
    0x4F: 'DIM',
    0x50: 'TAB',
    0x51: 'END',
    0x52: 'INPUT',
    0x53: 'INPUT',
    0x54: 'INPUT',
    0x55: 'FOR',
    0x56: '=',
    0x57: 'TO',
    0x58: 'STEP',
    0x59: 'NEXT',
    0x5A: ',',
    0x5B: 'RETURN',
    0x5C: 'GOSUB',
    0x5D: 'REM',
    0x5E: 'LET',
    0x5F: 'GOTO',
    0x60: 'IF',
    0x61: 'PRINT',
    0x62: 'PRINT',
    0x63: 'PRINT',
    0x64: 'POKE',
    0x65: ',',
    0x66: 'COLOR=',
    0x67: 'PLOT',
    0x68: ',',
    0x69: 'HLIN',
    0x6A: ',',
    0x6B: 'AT',
    0x6C: 'VLIN',
    0x6E: 'AT',
    0x6F: 'VTAB',
    0x70: '=',
    0x71: '=',
    0x72: ')',
    0x73: ')',
    0x74: 'LIST',
    0x76: 'LIST',
    0x77: 'POP',
    0x78: 'NODSP',
    0x79: 'NODSP',
    0x7A: 'NOTRACE',
    0x7B: 'DSP',
    0x7C: 'DSP',
    0x7D: 'TRACE',
    0x7E: 'PR#',
    0x7F: 'IN#'
};

export default class IntBasicDump
{
    constructor(private mem: Memory) {}

    private readByte(addr: word) {
        const page = addr >> 8,
            off = addr & 0xff;

        return this.mem.read(page, off);
    }

    private readWord(addr: word) {
        const lsb = this.readByte(addr);
        const msb = this.readByte(addr + 1);

        return (msb << 8) | lsb;
    }

    toString () {
        let str = '';
        let addr = this.readWord(0xca); // Start
        const himem = this.readWord(0x4c);
        do {
            /*var len = */this.readByte(addr++);
            const lineno = this.readWord(addr);
            addr += 2;

            str += lineno;
            str += ' ';
            let val = 0;
            do {
                val = this.readByte(addr++);
                if (val >= 0xB0 && val <= 0xB9) {
                    str += this.readWord(addr);
                    addr += 2;
                }
                else if (val < 0x80 && val > 0x01) {
                    const t = TOKENS[val];
                    if (t.length > 1)
                        str += ' ';
                    str += t;
                    if (t.length > 1)
                        str += ' ';
                }
                else if (val > 0x80)
                    str += LETTERS[val - 0x80];
            } while (val !== 0x01);
            str += '\n';
        } while (addr < himem);

        return str;
    }
}